I’m on the same boat. I have the KS 9.0. I have to add however the issue was pretty anywhere I was making phone calls over Bluetooth. Ie. car.
I had made several calls to Apple. Each call was pretty much the same steps. Restart the phone, Restart the HAs, reset the network settings, and then finally factory reset the phone completely. Most of these fix work for a short time ( I always suspected that it was just phone rebooting that would help ).
After the 4th call they finally asked me to send my phone in for repairs. When it came back the report in the box said they had replaced the speaker. No shocker, the problem was still the same. I called a 5th time and complained that the problem was still persisting. Long story short they replaced my phone and I’m still left with static during Bluetooth calls.
Either there is a major hardware flaw in the design of the Bluetooth for the iPhone 12 or there is iOS glitch. I’ve used my KS9.0 with the iPhone 6, 7, and X, as well as a couple of different iPads. I’ve never had any issues until now. It’s seriously such a shame.